Location and design of alpha magnet for speedometers



June 3, 1930. R. o. HELGEBY LOCATION AND DESIGN OF MAGNET FOR SPEEDOMETERS Filed June 18, 1928 Patented June 3, A 1960 UNITED STATES RALPH o. HELGEIBY, or 'rLIN'r, MICHIGAN,

ASSIGNOR TO A C SPARK PLUG COMPANY,

or FLINT, MICHIGAN, A COMPANY or MICHIGAN LOCATION AND DESIGN OF A MAGNET FOR SPEEDOMETERS Application filed June 18,

This invention relates to measuring instruments and has been designed particularly as an improvement in a magnetic speedometer.

An object of the invention is to provide a novel magnet and a novel supporting means for the magnet. The invention'also contemplates simplicity and economy by making the upper jewel frame integral w1th m the mounting plate by which the frame is secured to the casing. The invention also contemplates improvements in the driving mechanism and. in the die cast frame which carries the driving mechanism. Other obj ects and advantages will be apparent from a reading of the following description.

Tn the drawing:

Figure 1 is a view in front elevation of the instrument, the casing being removed Figure 2 is a transverse section on line 22 of Figure 1;

Figure 3 is a top plan view wlth the casing removed;

Figure 4 is a rear elevation, the casing being removed;

Figure 5 is a side view of the mechanism within the casing with the parts broken away; and

Figure 6 is a section on line 6-45 of Fig- .ure 4.

Referring by reference characters to the drawing, numeral 10 is used to designate a die cast frame. This frame is used to carry the movable parts of both a speedometer and an odometer, as usual. To the frame is riveted or otherwise secured a so-called mounting plate 12 of substantially annular shape. This plate 12 locates the die cast frame within an enclosing casing 14. The plate 12 engages a casing flange 11. Outside the mounting plate 12 is a dial plate 13 and a glass 15. A bezel 17 clamps around and holds these parts assembled.

Formed as an integral part of stamped plate 12 is an angular jewel frame 16. This jewel frame has a hair spring holder 18, as shown in Figure 2. It has also formed as an integral part thereof a speed cut stop 20, a spindle retainer 22 and a hole jewel seat 24. By making part 16 integral with 1928. Serial 110. 286,451.

12 and the parts 18, 20 and 22 as integral parts of plate 16, considerable economy in manufacture and assembly is made The magnet 26 is of U-sha e and is positioned horizontally around t e usual s ed cup 28. The center of the arc portion '0 the magnet is in the axis of rotation of the speed cup. By this means the magnetic lines of force are most effectively used. At 30 is a strap of non-magnetic material. It embraces the magnet and holds it in position on the frame 10, there being terminal ears 32 to snap over outwardly directed lugs 34 formed as parts of the die cast frame.

The legs of the magnet 36 are cut at an angle 5 at their ends and engage similarly shaped stops on the frame. The magnet rests on a rib 38 and is held firmly seated on the rib and against the frame stop when the strap 30 is snapped into position.

Numeral 40 is the so-called first worm or rotor shaft. It has an hexagonal hole in its lower end to receive the similarly shaped drive tip 42. By the use of an openin of this shape, the tip is very easily assem led with the rotor or first worm. shaft 40. As shown in Figure 2, the rotor shaft carries a rotor member 21 which is rotatable within the speed cup and magnet. The upper end of the rotor shaft is hollowed out to carry the lower end bearings for the spindle 23 of the speed cup 28. The rotor shaft has an intermediate gear portion as at 25 both above and below which the shaft is journaled in the frame. This not only accurately positions the shaft for engagement with the second worm, but also maintains the lower jewel bearing for the speed cup spindle in accurate location. The rotor shaft is held in position by a clip or retainer 44 entered through a slot 46 in frame 10 and received within a groove 48 in the shaft. A cotter pin 50 may be used to retain part 44 in position.

The second worm 52 is located behind and at right angles to the first worm. This second worm is rotatable on a shaft 62 pressed into bosses 64, these bosses being integral parts of frame 10. The second worm 52 turns freely on shaft 62, being supported by Jun shaft 62 throughout thelength of the worm.- By this means a long frame bearing for the rotating second worm is not needed and a saving of material in the die cast frame is thereby made. This has a further advantage of making a simpler die casting. Owing to its long bearing on shaft 62, the second worm is accurately positioned with relation to the first worm.

For driving the odometer mechanism, the second worm has a terminal eccentric 54:. This eccentric oscillates a awl 56 which rotates a ratchet wheel 58. 1E spring 60, which may be riveted to frame 10, engages and holds the pawl 56 upon the ratchet. The driven ratchet drives through the conventional transfer mechanism the dial wheels 31 of the season set, and b means of an idler 33, gear 35 and clutch 3 the wheels 39 of the trip; set are driven. As usual, a reset including a stem 41 is used with the trip set. These parts-are conventional, not a part of this invention and are not, for this reason,

- more specifically described.

By locating the magnet horizontally around the speed cup and coaxial therewith, a more efiicient speed measuring unit is obtained as the entire magnetic field surrounds the speed cup. The magnet drag is much greater than is obtainable with a vertically positioned fixed magnet. The fastening means including the angled ends of the magnet and the strap affords a very simply assembled arrangement to hold the magnet firmly upon its seat on the frame. The arrangement by which the strap is merely snapped into position avoids the use of screws, rivets, or other fastening means.

The number of parts is considerably reduced by making the upper jewel frame 16 integral with the mounting plate, a further simplification being effected by sha ing the plate 16 to perform the several unctions enumerated.

The hexagonal hole in the first worm shaft makes it ver easy to assemble the tip of the driving shaft.

By locating the second worm 52 behind the first worm 25 and by providing in the frame bearings for both ends of the first worm, a very desirable distribution of side thrust is had and a very accurate positioning of the rotating jewel for the lower end of the speed cup spindle.

The quantity of metal in the die cast frame is reduced by the expedient whereby shaft 62 is carried in'frame lugs and the second worm is rotatabl mounted throughout its length on the sai shaft 62..

I claim:

1. In a magnetic measuring instrument, a rotatable speed indicating member, a U- shaped stationary magnet, the arc-shaped portion of the magnet surrounding'and belng concentric with said speed indicating member the speed indicatin member being in the form of a cup exten ing beyond the legs of said magnet.

2. In a magnetic measuring instrument, a supporting frame a magnet, said magnet being of U-shape, t 1e ma net supported upon said frame, and the en s of the legs" engaging walls on said frame to position the magnet, and means in the plane of said magnet, embracing said magnet and detachably engaging said frame to hold the magnet in position.

3. The invention defined by claim 2, said last-named means being a strap of non-ma netic material having ears for detachab y engaging frame lugs.

4. In a ma 'netic measuring instrument, a supporting rame, a magnet, said magnet being of U-shape, the magnet supported upon said frame, and the ends of the legs engaging walls on said frame to position the magnet, and means embracing said magnet and' detachably engaging said frame to hold the magnet in position, the ends of the legs of'said' magnet and the co-operating faces ofsaid frame in abutment with the magnet ends being parallel and at an acute angle to the axis of said magnet whereby said holding means wedges said magnet firmly into position.

5. In a magnetic measuring instrument including a casing, an instrument carryin frame and an indicating member mounte on a rotatable spindle, a mounting plate secured to said frame and locating said frame in said casing, a top plate integral with said mounting plate and serving as an upper jewel carrier for the rotating spindle.

6. The invention defined by claim 5, said ,top plate further shaped to serve as a stop to limit the rotation of the indicating means and as a retainer to prevent axial movement of said spindle.

In testimony whereof I aflix m signature.

- RALPH O. HE GEBY. 

